Hitherto, various means have been used as information providing means for providing a passenger of a mobile body such as a vehicle with route guidance and drive information such as a warning of an obstacle. Examples of such means include display on a liquid crystal display installed in the mobile body and audio output from a speaker. In recent years, a head-up display device (hereinafter referred to as an “HUD”) has been provided as an example of the information providing means.
As described in Japanese Patent Application Publication No. 2009-288388 (JP 2009-288388 A), an HUD installed in a vehicle, in particular, as an example of a mobile body can generate a virtual image as superimposed on the foreground in the forward field of view ahead of a window (e.g. the windshield) of the vehicle as seen from a passenger of the vehicle. As a result, it is possible to reduce movement of the line of vision as much as possible when the passenger visually recognizes the drive information, and to reduce a burden during drive.